1. Field of the Invention
The present invention relates to an apparatus for processing an inside of pipe and a method of processing an inside of pipe for performing works such as rinse, inspection, examination, preventive maintenance, repair, and the like of an inside of a pipe, and, more particularly, to an apparatus and method for processing an inside of pipe for performing necessary works such as rinse, inspection, examination, preventive maintenance, repair, and the like of an inside of a pipe with respect to a welding line of a jet pump installed in a pressure vessel of a boiling water reactor.
2. Related Art
Works such as rinse, inspection, examination, preventive maintenance, repair, and the like of an inside of a pipe in a jet pump installed in a pressure vessel of a boiling water reactor must be performed under radiation environmental conditions. Further, since a person cannot access the pipe and a working environment cannot be secured, there is proposed a system (inspection without disassembly) for performing inspection and examination works by inserting a pipe inside processing apparatus into the pipe without removing an inlet mixer of the jet pump to reduce man-hour and working time.
Most of known technologies employ pipe inside processing apparatus, which have a structure for fixing the apparatus and hold them on an inside of a pipe by a plurality of arms that can be developed in a radial direction, and also employ pipe inside processing methods using the apparatus.
As an example of such apparatus for inspecting and examining an inside of the jet pump, there is proposed a pipe inside processing apparatus, which has a slender casing and the position of the apparatus is held in a pipe by developing a plurality of arms from the apparatus in a radial direction, and further a pipe inside processing method using the apparatus (refer to, for example, Patent document 1: Japanese Unexamined Patent Application Publications No. 2001-281386 and Patent document 2: Japanese Unexamined Patent Application Publication No. 2001-159696).
The Patent Document 1 employs a structure for developing a pair of arms driven by an air cylinder in an inside of a pipe to position a work unit composed to a pipe inside scraper and a suction port.
Further, the Patent Document 2 fixes a pipe inside processing apparatus by developing three arms driven by an air cylinder to position the processing apparatus in the inside of the pipe. Then, the processing apparatus is moved to and held by the inside of the pipe by a link mechanism and an articulated arm disposed to a lower portion of the apparatus.
Further, a Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2001-65778) proposes a pipe inside processing apparatus for holding the position of arms in a pipe by develop a plurality of guide arms from a slender casing in a radial direction. In the example, the guide arms are developed and fixed in three directions in an inside of a pipe by disposing detectors to the extreme ends of three legs developed mechanically. Thereafter, the processing apparatus is rotated in the inside of the pipe using a cable as a fixing side. Further, a weight is coupled with a lower end of the apparatus to stabilize the position thereof and can be disposed in parallel with the center axis of the apparatus.
As described above, almost all the structures for fixing the pipe inside processing apparatuses to the inside of the pipe fix the processing apparatuses by pressing them against the inside of the pipe by developing a plurality of arms in a radial direction.
In the pipe inside processing apparatus having the fixing structure as described above, when the extreme ends of the plurality of arms are inclined because the normal line of a plane, including the points at which the extreme ends of the plurality of arms come into contact with the inside of the pipe, becomes out of parallel with the axis center of the pipe, the rotation surface of an inspection sensor along the circumferential direction of the pipe is offset obliquely, and the sensor is offset from a horizontal welding line. Accordingly, there arises a problem in that the inspection sensor cannot perform desired inspection and examination.
Further, when the pipe inside processing apparatus is raised or lowered in its entirety to correct the offset center axis thereof, the relative up/down positions of the pipe and the inside of pipe processing apparatus may be offset from each other or the inspection sensor may be offset from the horizontal welding line. Accordingly, it cannot perform desired inspection and examination. Since it is necessary for an articulated arm having a multiplicity of degrees of freedom to correct the offset amount and to move the inspection sensor in the circumferential direction along the inside of the pipe, the structure of the processing apparatus is made complex and the size thereof is increased. Thus, there arises a problem in that the apparatus cannot pass through the opening between a nozzle and a throat of the jet pump.
Furthermore, when the number of parts of the pipe inside processing apparatus is increased, there is a tendency that a risk of occurrence of failure also increases. As a result, there is an increased risk that the arm cannot be closed because the pipe inside processing apparatus fails and cannot be collected from the opening between a nozzle and a throat of the jet pump. Further, even if the processing apparatus can be collected, there is a high possibility of damaging the nozzle and the throat of the jet pump.